Process of spinning viscose



Patented Apr. 6, 1943 PROCESS OF SPINNING VISCOSE Johann Joseph Stoeckly, Teltow-Seehof, and Wolfgang, Linnhoff, Berlin-Lankwitz, Germany, assignors to North American Rayon Con.

poration, New York, N. Y., a

Delaware corporation of N Drawing. Application June 15, 1939, Serial No. 279,360. In Germany June 16, 1938 18 Claims.

The present invention relates to a process of producing high-strength filaments, threads, yarns, etc., from viscose solutions.

The primary object of this invention relates to a process of projecting viscose solutions into a spin bath containing a soluble iron salt besides conventional bath ingredients.

Another object of this invention relates to a process of extruding a viscose solution into an acid spin bath containing iron sulphate to produce yarns having improved tensile strength, toughness and elasticity. I

A further object of this invention has to do with a viscose spinning process which comprises extruding a viscose solution into a primary, acid spin bath containing a soluble iron salt and stretching the filaments, threads. yarns, etc., thus formed in a secondary bath maintained at an elevated temperature.

Other objects of this invention will become apparent to those skilled in the art from a study of the following specification.

We are well aware that it has, heretofore, been proposed to spin viscose solutions into primary spin baths containing soluble zinc salts, such as, for example. zinc sulphate, and to stretch the coagulated products in a secondary bath maintained at a temperature of at least 60 C. in order to obtain artificial silk having especially favorable physical characteristics (vide British Patent #467,500 to- Courtaulds Ltd). However,

, such zinc-bearing baths are deficient in that they impart to regenerated cellulose a high strength in dry and wet condition.

We have, unexpectedly, found by experimentation that the aforementioned deficiency of zinc bathscan be overcome by using a primary spin bath containing soluble iron salts, such as iron 7 sulphate, etc. The amount of iron in the primary bath may be varied within wide limits, although we have found that about to 50 grams of an iron salt, for example, iron sulphate, per liter of bath are generally sufficient to give the desired result. However we do not wish to be limited to this amount .since'it may be lowered or raised inorder to vary the physical characteristics of the artificial silk spun-in the bath. In this manner. ibis possible to obtain viscose yarns, staple This deficiency,

fibers, etc., from conventional viscose solutions having a dry strength of about 300 to 340 grams per 100 den., and a wetstrength of about 190 to 200 grams per 100 den. The strength of the regenerated cellulose may naturally be modified by using special viscose solutions. Such special viscose solutions may contain lower or higher amounts of cellulose and/or be less ripened than conventional viscose solutions.

The aforementioned effect of iron salts in the primary spin bath, however, is only obtained when the initial products formed therein are stretched in a hot, secondary spin bath. In other words, it is not possible to eliminate the iron salt from the primary bath and to stretch the yarn, etc., to the same degree in the hot secondary spin bath. When a viscose solution is projected .cordance with our novel process.

into a primary spin bath devoid of iron to form an initial thread and this thread is then given the maximum stretch in a hot, secondary bath, the final" thread will have less strength'than threads of regenerated cellulose obtained in ac- The beneficial effect of iron in the. primary bath is bound to the stretching in the hot, secondary bath. This effect becomes noticeable at a temperature of about C. and pronounced at a temperature of about C. However, the secondary bath may have a temperature of and attain even the boiling point of water.

We are well aware that it has, heretofore; been recommended to add soluble iron salts, such as iron sulphate, iron nitrate, iron nitrite, ferrous ammonium sulphate, ferric ammonium sulphate, etc., to spin baths in order to somewhat eliminate hydrogen sulphide generated during the spinning of viscose. However, it could not be foreseen by those skilled in the art that iron in the primary bath hasthe property of promoting the stretching in a hot, secondary bath, this stretching resulting in especially strong end products. Furthermore, it could not be foreseen that spin baths containing soluble iron salts, especially iron sulphate, reduce the clogging of spinneret orifices in comparison with Zinc-bearing spin baths. This reduction in clogging of spinneret orifices results in a reduction of spinneret change during the production of viscose products. When conventional, acid spin baths containing about '50' grams of zinc sulphate per literare used, a con-' I siderable clogging of the orifices of noble metal to 30% by the formation of so-called zinc rings? When the novel'spin baths, containing for examwhereby incrustation of the orifices of 2 ple 50 grams of iron sulphate and-no zinc-sul phate are used the spinneret orifices are not clogged after six hours of spinning. There is no formation of corresponding iron rings.

Example A conventional viscose solution, containing about 7.2% cellulose and 6.5% alkali and ma-- tured to 125 (H), is spun into a primary spin" bath at a temperature of about 50 C. The bath travel is about 20 cm. The primary bath ,con-

tains about 125 g. of sulphuric acid, 260 g. of

sodium sulphate and 50 g. of iron sulphate per liter of water. -Th e thread is continuously stretched about 80% by means of driven rollers in a ,secondary bathmaintained at atemperasolution through minute" amass 'tion through minute orifices of a metal spin neret intoan acid coagulating bath devoid of zinc and containing .a soluble iron salt in an ture of about 85. The first roller has a speed I of about 33.5 meters per minute and the second J one a speed of about GOVmetersper minute. The

secondary bath may consist of pure water or it may contain small amounts of the ingredients of Y the primary bath. These ingredients may be carried over by the thread from the primary to the secondary bath. The thread thus produced has the following physical characteristics:

Dry strength per 100 den.; 300440 g. Wet strength per 100 den.: 190-200 g.

Although we prefer to use iron sulphate for reasons of economy in our spinning process, we

wish to emphasize that it may be replaced by any iron salt sufficientlysoluble and stable in. spin baths conventionally used in the viscose art. Modifications of our. invention will readily be recognized by those skilled-in the art, and we desire to include all such modifications and variationscoming within the scope of the appended claims.

We claim: a Y

1. In a process of spinning viscose rayon. the

amount'sufilcient to delay the decomposition to cellulose hydrate and then stretching the yarn in excess of 40% while subjecting the yarn being stretched to the action of an aqueous-heat-' ing liquid at a temperature above 60 0., whereby incrustation of the orifices of said spinneret is substantially inhibited. v

6. In a process of spinning viscose rayon, the

steps which comprise projecting a viscose solution through minute orifices of a metal spin-' neret into an acid coagulating bath devoid'oi zinc and containing a soluble iron salt in anamount'suificient to delay the decomposition to cellulose hydrate and then stretching the yarn about 80% while subjecting the yarn being stretched to the action of an aqueous heatins liquid at a temperature above 60 0., whereby lncrustation of the orifices of said spinneret is steps which comprise projecting the spinning solution through minute orifices of a metal spinneret into an acid coagulating bath devoid of ZIJC and containing a soluble iron salt in an amount suificient to delay the decomposition to cellulose hydrate and then stretching, the freshly spun yarn while subjecting the yarn being stretchedto the action of an aqueous heating liquid at a temperature above 60 C., whereby incrustatiomof the orifices of said spinneret is substantially inhibited.

2. In a process of spinning viscose rayon, steps which comprise projecting the spinning. solution through minute orifices of a metal spin neret into an acid coagulating bath devoid of zinc and containing from about v15 to g. of a soluble iron salt per liter of bath and then stretching the freshly spun yarn while subjecting the yarn being stretched to the action of an aqueous heating liquid at a temperature above 0., whereby inprustation of the orifices of st id spinneret is substantially inhibited- 3. In a process of spinning viscose rayon, the

substantially inhibited. f

, 7. In a'process of spinning viscose rayon, the steps which comprise projecting a viscose solution through minute orifices of a metal spinneret into an acidcoagulating bath devoid of zinc and containin? iron sulphate in an amount sufilcient'to delay the decomposition to cellulose hydrate and then stretching the yarn about 80% while subjecting the yarn being stretchedto' the action of an-aqueous heating liquid at a temperature above 60 0., whereby incrustation of the orifices of said spinneret is substantially 8. In a process ,of spinning viscose rayon, the steps which comprise projecting the spinning solution through minute orifices of a metal spin-.- f

neret into an acidcoagulating bath devoid of zinc and containing a soluble iron salt in anamount sumcient to delay the decomposition to cellulose hydrate and then stretching the freshly spun yarn while subjecting the yarn being stretched to the action of water at a temper-sag ture above 60 0., whereby incrustation of the or fices of said spinneret is substantially i f hibited. ,7 9. In a process ofspinning viscose r ,the steps which comprise projecting the spinning solution through minute orifices of a metal spinneret into an acid coagulating bath devbld or steps which comprise projecting the spinning solution through minute orifices of a metal spin-' neret into an acid coagulating bath devoid of,

zinc and containing from about 15 to 50 g. of iron sulphate per liter of bath and then stretching the freshly spun yarn while subjecting the yarn being stretched to the action of an aqueous neating liquid at a temperature above 60 C";

neret is substantially inhibited.

said spin- 4. In a process of spinning visc se rayon, the

steps which comprise projecting the spinnin zinc and containing from about 15 to 50g. of a soluble iron salt per liter of bath and then stretching the freshly spun yarn while s,ubJect-' -ing the yarn being'stretched to the action of water at a temperature above 60 C., whereby incrustation of the orifices of said spinneret is substantially inhibited.

v 10. In a process of spinning viscose rayon, the

steps which comprise projecting the spinning; solution through minute orifices'of a metal spin- -neret into an acid coagulating bath devoid of zinc and containing from about 15 .to 50 g. of

iron sulphate per liter of bath and then stretching the freshly spun yarn while subjecting the yarn being stretched to the action of water at a temperature above 60 0., whereby incrustation of the orifices of said spinneret is substantially inhibited.

11. In a process of spinning viscose rayon, the steps which comprise projecting the spinning solution through minute orifices of a metal spinneret into an acid coagulating bath devoid of zinc and then stretching the freshly spun yarn while subjecting the yarn being stretched to the action of water at a temperature above 60 C., said coagulating bath containing about 125 g. of sulphuric acid, about 260 g. of sodium sulphate and about 50 g. of iron sulphate per liter of water, whereby incrustation of the orifices of said spinneret is substantially inhibited.

12. In a process of spinning viscose rayon, the steps which comprise projecting a viscose solution through minute orifices of a 'metal spinneret into an acid coagulating bath devoid of zinc and containing a soluble iron salt in an amount sufilcient to delay the decomposition to cellulose hydrate and then stretching the yarn in excess of 40% while subjecting the yarn being stretched to the action of water at a temperature above 60 0., whereby incrustation of the orifices of said spinneret is substantially inhibited.

13. In a process of spinning viscose rayon, the steps which comprise projecting a viscose solution through minute orifices of a metal spinneret into an acid coagulating bath devoid of zinc and containing a soluble iron salt in an amount suiilcient to delay the decomposition to cellulose hydrate and then stretching the yarn about 80% while subjecting the yarn being stretched to the action of water at a temperature above 0., whereby incrustation of the orifices of said spinneret is substantially inhibited.

. 14. In a process of spinning viscose rayon, the steps which comprise projecting a viscose solution through minute orifices of a metal spinneret into an acid coagulating bath devoid of zinc and containing iron sulphate in an amount sufficient to delay the decomposition to cellulose hydrate and then stretching the yarn about while subjecting the yarn being stretched to the action of water at a. temperature above 60 (1., whereby incrustation of the orifices of said spinneret is substantially inhibited.

15. A viscose spin bath containing about g.

of sulphuric acid, at least 15 g. of a soluble iron salt and about 260 g. of sodium sulphate per liter of water, said bath being devoid of zinc.

16'. A viscose spin bath containing about 125 g. of sulphuric acid, at least 15 g. of iron sulphate and about 260 g. of sodium sulphate per liter of water, said bath being devoid of zinc.

17. A viscose spin bath containing about 125 g. of sulphuric acid, about 50 g. of a soluble iron salt and about 260 g. of sodium sulphate per liter of water, said bath being devoid of zinc.

18. A viscose spin bath containing sulphuric acid, sodium sulphate and at least 15 grams of a soluble iron .salt per liter of water, said bath being devoid of zinc.

JOHANN JOSEPH STOECKLY. WOLFGANG LINNHOFF.

CERTIFICATE OF comm-Ion. Patent No. 2,51 ,5 9, April 6, 19h

JOHANN JOSEPH STOECKLY, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered. patent 'requirlng correction as follows: Page 2, first column, lines 50, 61 and 72, and second co1umn, l1nes 9, 22, 5b., 14.5,.57 an'd 69, pegej first column, lines 14., 17 and 28, and seconcl column, lines 14. and 16, claims 1 to 1b. inclusive, fer 'lncrustation read clogging; and that the acid Letters Patent should .be read. with this correction thereinthet the same may conform to the record of the case inthe Patent Office. a

Signed and sealed this 25th day of Play, A" n. 1915,

. Henry Van A'rsdale; (Seal) 7 Acting Commissioner of Patents. 

